You can provide a handler for the OnGetMarkText event of the x axis. It gets the x value (minutes, in your case) and returns the displayed text. So, if the user wants to see minutes, don't use this handler. But if he wants to see days.hours:minutes you can hook the handler to the event, do the conversion and return the result in the handler. Not 100% sure, but you may have to adjust the Chart.BottomAxis.Intervals.MaxLength to avoid overlapping labels when switching between these two cases.